Along an assembly line, various types of articles, such as for example, diapers and other absorbent articles, may be assembled by adding components to and otherwise modifying an advancing, continuous web of material. For example, in some processes, advancing webs of material are combined with other advancing webs of material. In other examples, individual components created from advancing webs of material are combined with advancing webs of material, which in turn, are then combined with other advancing webs of material. Webs of material and component parts used to manufacture diapers may include: backsheets, topsheet, absorbent cores, front and/or back ears, fastener components, and various types of elastic webs and components such as leg elastics, barrier leg cuff elastics, and waist elastics. Once the desired component parts are assembled, the advancing web(s) and component parts are subjected to a final knife cut to separate the web(s) into discrete diapers or other absorbent articles. The discrete diapers or absorbent articles may also then be folded and packaged.
Various methods and apparatuses may be used for attaching different components to the advancing web and/or otherwise modify the advancing web. For example, some production operations are configured to apply relatively high viscosity fluids, such as hot melt adhesives, to an advancing web. In some instances, the production operations are configured to apply hot melt adhesives to an advancing web in pre-determined patterns. These operations may include the use of systems and methods such as slot die coating, direct gravure, offset gravure and reverse gravure roll coating processes that are extensively described in the art. However, current systems and methods for applying patterned adhesives to an advancing substrate may have certain limitations.
For example, in the manufacture of absorbent articles such as feminine hygiene pads, baby diapers, and adult incontinence pads, the use of gravure coating processes may be confounded by contamination of the impression cylinders by fibers separated from the substrates to be coated. Some problems associated with gravure cavities and incomplete fluid transfer are described, for example, in U.S. Pat. Nos. 7,611,582 B2 and 6,003,513. In some instances, slot die coating may be used for patterned coating of webs in the manufacture of absorbent products. The use of combed shims in slot die transfer processes can provide fine resolution and precise transfer of fluid to the receiving substrate in the axis transverse to the direction of web travel. Such slot transfer processes may also be configured with electro-pneumatic switching valves to intermittently transfer adhesive to an advancing substrate. However, the quality and precision of intermittent transfer of fluids to an advancing substrate may be limited by the speed of the on/off cycle of switching valves used to interrupt the flow of fluid to the slot die of the fluid applicator. Thus, as web processing speeds increase, the ability of current slot die coating methods to achieve fine resolution of on/off coat patterns in the direction of web travel decreases. Consequently, it would be beneficial to provide apparatuses and methods that apply adhesives and other fluids to a substrate in patterns with relatively high resolution and high speeds without being limited by the speed of on/off cycling of switching valves used to interrupt the flow of fluid to the slot die of the fluid applicator.